I've been kicking an idea around for awhile and did a google-search but
couldn't find anything directly on point. A recent post about peltier
devices made me think about this again. What about coupling a peltier
with a heatpipe?

For those who don't know, a 'heat pipe' is a very simple device with no
moving parts and requiring no power, but which helps transfer heat from
one place to another. In its simplest form, it would be a length of
straight copper pipe sealed at both ends, partially filled with alcohol
or freon or some other liquid to act as a refrigerant. To cool a
carboy, it would be inserted into the neck of the carboy and extend from
the bottom and protrude through the neck for some distance -- perhaps a
foot (30cm) or a bit more. The liquid refrigerant (alcohol, freon, or
whatever) pools at the bottom of the pipe, picks up heat from the
fermenting wort which causes some of the refrigerant to evaporate and
rise to the top (into the part of pipe extending outside the carboy)
where it condenses, releasing heat to the upper part of the pipe where
it is dissipated into the air, and the condensed refrigerant runs back
down the pipe into the lower portion within the carboy to repeat. The
cycle is continuous so long as there is a temperature differential,
helping move heat from the inside to the outside of the carboy. The
thinnest gauge copper would be used to improve conductivity, and even
convoluted pipe could be used to increase surface area and efficiency.

By itself, I'm not sure a heatpipe would help very much because it can't
cool below ambient temperature, and I can do better than that with a fan
and evaporative cooling. But heatpipe performance should be improved
immensely by adding a peltier device to the top portion of the pipe, and
I think it would probably lower temps more than evaporative cooling,
based on my readings. For those who don't know, a peltier device uses
solid state electronics and a flow of direct current to move heat from
one side to the other; an example is those ice chests which can be
plugged into a car's cigarette lighter socket. Coupling a peltier to a
heatpipe would also solve a couple of problems for people who want to
use a peltier with a carboy: first, it solves the problem of how to
connect to the carboy; second, it reaches to the center of the wort
which is hardest to cool; third, because it runs up the center,
convective currents should be uniformly distributed within the fermenter
for greater efficiency and uniformity of temperature. The pipe would be
easy to sanitize and since it isn't permanently mounted, the whole thing
could easily be moved to other fermenters such as a bucket or a conical,
if they have a sufficient opening in their lids. A thermostatic
coupling for the peltier could run along the side of the pipe, thereby
measuring temp at the center of the fermenter to regulate the peltier.

There are some downsides, but nothing significant in my mind. First,
you won't be able to use a Burton Union on your carboy, but I don't know
anyone who does anyway, even though they are available. Second, you
won't be able to use a blow off tube or a conventional airlock. How bad
is that? Well, if properly designed, the heatpipe should act as an
airlock itself. If the pipe has a flange or is widened at the point
where it enters the fermenter so that the weight of the pipe rests on a
sanitized rubber gasket between it and the lid or carboy neck, I think
it will provide a sufficient seal. Pressure inside the fermenter would
merely lift the entire pipe and peltier device just enough to release
CO2, and whenever it vents in that way, the positive pressure inside the
fermenter should prevent oxygen and contaminants from entering.

Would that create too much pressure inside the fermenter, risking an
explosion of the carboy? Most of the weight of the portion of the pipe
which is submerged in wort would be offset by buoyancy; in fact,
depending upon the gauge of the pipe and how much it is filled with
refrigerant, that portion of the pipe might even have a positive
buoyancy. That leaves the portion of pipe extending above the level of
wort, plus the weight of the peltier, heat sink (if any), and fan. I've
tried to find some weight specifications to use as examples, but
unfortunately haven't found any yet. But some of these devices that are
available are mounted on CPUs inside computers, and don't look like they
could weigh much more than a pound -- but let's use 3 pounds (1.36kg) as
an example and as an upper limit of total negative buoyancy, i.e., the
weight on the gasket at the carboy neck or lid. The inside diameter of
the neck on my carboys is about one and an eighth inches (2.86cm), for a
surface area of .994 square inches (6.41 square cm) -- "close enough for
government work" to call one square inch. Assuming three pounds of
weight on that one square inch, it would require 3 psi to break the
seal, causing a pressure of 3psi throughout the carboy. I tried to
research whether that was too much or not, and couldn't find an answer;
I did find this thread -- http://tinyurl.com/fvned -- which was
inconclusive. But assuming that 3psi is not too much, the pipe and
peltier should cause a good seal. Now, another bad downside with not
being able to use a blow off tube is that, with a really vigorous
fermentation, each time the seal is momentarily broken to vent pressure,
we're likely to have some kraeusen squirt out; this can at least be
deflected downward by adding to the heatpipe a small sleeve which
overhangs the neck of the carboy, but then we would still have a mess
with kraeusen running down the sides of the carboy -- although it could
be set inside a small pan or tub to minimize the mess. However, if the
heatpipe and peltier are successful in holding the temp of the wort down
to a nice low temp of, let's say, 64F/18C, will fermentations really be
that vigorous? I don't know because I've never been able to ferment
that low; I've had some pretty violent fermentations, but I've seldom
been able to keep my temp down below 70F/21C. With lower temps,
fermentations will be slower, but I don't know how slow.

This is just some thinking on my part; I've never attempted any of this
and don't know if it would work or not. Seems to me like it would, and
I'd love for some of the more knowledgeable engineering types here to
comment on this. If anyone thinks they can make this work and market
it, you have my permission; just send me a 'beta' unit to try out. ;-)
Also, if anyone tries this, please let me know how it works out. I
might give it a try myself, but I'll need to find out a lot more about
how to make the heat pipe -- how much liquid to put in it, etc. But
there's no sense in even trying if calculations say it won't work.

I'm cross-posting to relevant forums because people tell me that that's
what I should do instead of single-posting; I get arguments both ways.
Also, I'm sorry this is so long; I hope you folks don't mind.

Thanks.

Cheers, Bill Velek
Join "HomeBrewers" international grid-computing team and help mankind by
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Bill ,

Interesting ideas, but evaporative cooling is more than adequate for my
purposes (winemaking). And if that weren't enough, I'd probably trickle
50°F well water over the carboy (how's that for efficiency?: geothermal
cooling).

My one thought on your heat pipe setup is that you might well want to
limit the contact between copper and an acid medium like wine. Beer
might be a different matter, but wine dissolves copper, brass, iron,
aluminum, etc. and prolonged contact often imparts metallic tastes and
worse. I once ruined a batch of blueberry wine by leaving a metal (non
stainless) spoon in it for about a week.

Sounds like fun though. Let us know how it turns out.

--
Mike MTM, Cokesbury, NJ, USA

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Bill Velek wrote:
> I've been kicking an idea around for awhile and did a google-search but
> couldn't find anything directly on point. A recent post about peltier
> devices made me think about this again. What about coupling a peltier
> with a heatpipe?
>

Well it is worth a shot, that is for sure. It sounds like a glycol
chiller. A good fluid to put inside the pipe would be antifreeze since
it can go below freezing if need be (like you could use it to double as
a wort chiller maybe).

Just as an aside (since you posted this in winemaking asn meadmaking) I
would think about avoiding copper in acidic environments, just so you
do not have the problem of oxides ending up in your beverage...and
acids often found in wine and mead (even if in small amounts) can react
with copper (IIRC, ask a metalurgist to be sure, I do beleive there is
one around *wink wink*) forming toxic salts, like verdigris.

True, but stainless would work, and there are folks who sell steel
Hypodermic Needle tubing with very thin walls.

Personally, not a big problem for me, but I live where it usually isn't
too hot outside during fermentation season, and my batches aren't big
enough to need such cooling.

Very cool idea, though.

Rob

"Bill Velek" > wrote in message
...
> I've been kicking an idea around for awhile and did a google-search but
> couldn't find anything directly on point. A recent post about peltier
> devices made me think about this again. What about coupling a peltier
> with a heatpipe?

I think the idea has a lot of merit.
My question is, the influence of ambient temperature. Like most
refrigeration, the colder you can keep the hot side, in this case the top of
the pipe, the colder the cold side runs (the bottom of the pipe). I could
see it (in theory) working in my winter but not in summer.
Adding a peltier device has the same consequences as you are now using two
refrigeration devices. The colder the hot side runs the colder the cold side
runs. In other words forget about how low the temperature can go but work
instead on how much lower than ambient can the device cool, and thats tough
and would involve a lot of math.
Steve W (in Aus).

(reply x-posted)

What you're describing is no different than the glycol chillers used in most
breweries today, but you want to replace the unit that does the cooling with
a Peltier device for greater efficiency. I've considered this many times in
the past as well but never bothered to build the beast.

Also, you'll want to use a pump to recirculate the refrigerant to maximize
the chilling for the amount of stainless tubing you use. You don't have to
use a pump, but if you rely on the action of your refrigerant to do the
circulation for you, you won't get nearly as much chilling power for the
amount of tubing you want to use.

To deal with your other issues regarding the carboy. It's always been my
thought to build this chiller using a plastic pail or stainless steel pot
with holes cut in the top with the two lines from the chiller going through
the lid, with the lid suspending the weight of the chiller. Again, not much
different than commerical glycol chillers.

Cheers,
Scott

Rob wrote:

> True, but stainless would work, and there are folks who sell steel
> Hypodermic Needle tubing with very thin walls.
>
> Personally, not a big problem for me, but I live where it usually isn't
> too hot outside during fermentation season, and my batches aren't big
> enough to need such cooling.
>
> Very cool idea, though.
>
> Rob

Thanks, Rob, for the encouraging words. Also a thank you to Mike and
Droppy for pointing out the problem with copper, and to the other
posters for their comments, too. I'll just cover everything in this one
post.

So long as the reduced thermal conductivity doesn't present a problem,
stainless would be fine in place of copper.

When Scott pointed out that, without a pump, the amount of pipe within
the fermenter may not be adequate for the amount of heat to be moved, he
may well have hit the nail on the head, but I'd like to see if I can
locate some precise figures or a formula or something like that. That
was one of the main questions that I'm researching -- how efficient is a
heat pipe, and how can I build or acquire one if one should work? The
question has never, in my mind, been about the peltier.

Cheers, Bill Velek
Join "HomeBrewers" international grid-computing team and help mankind by
donating spare computer power for medical research such as cancer; we're
in the top 8%, and we beat the MillerTime team: http://tinyurl.com/b7ofs
The life that your computer can help save ... might be someone you love.

We used to use peltier devices as a passive cooling system for the
military back in the 60's. We built the first ones where I used to
work; they were heat pipes in effect. They are not very efficient from
an electricity usage standpoint, are affected by ambient conditions;
they are rated by temperature across the faces at a given current.

You did hit the nail on the head when you questioned the heat transfer
required if placed into a carboy. Your surface to mass ratio with any
material is too low if you intend to insert it into a carboy. You
can't use copper or copper bearing alloys in winemaking as you know
from others so the thermal conductivity will be lower to make matters
worse.

If you wrap the tubing around the carboy that might be another matter
but all of this would turn out to be an expensive proposition.

If you live in an area where the relative humidity is low the
evaporative cooling idea sounds good, you could wrap a towel around the
carboy and drip water onto it and blow a fan across it to improve the
efficiency.

If you are willing to pump fluid you may be able to place a tank in a
refrigerator or freezer and pump fluid out through copper tubing
wrapped around a carboy foamed over with an insulation package.

I apologize for not giving you values but I just can't see it working;
you can gather thermal conductivity data from the CRC handbooks, any
version would do. That won't be the issue. The available surface area
of the tubing inserted and in contact with the wine will be the issue
no matter how cold you can get the liquid in the tubing or how fast it
flows.

Joe

> So long as the reduced thermal conductivity doesn't present a problem,
> stainless would be fine in place of copper.
>
> When Scott pointed out that, without a pump, the amount of pipe within
> the fermenter may not be adequate for the amount of heat to be moved, he
> may well have hit the nail on the head, but I'd like to see if I can
> locate some precise figures or a formula or something like that. That
> was one of the main questions that I'm researching

"Bill Velek" > wrote in message
news:2d1e9$43fae079
>
> So long as the reduced thermal conductivity doesn't present a problem,
> stainless would be fine in place of copper.
>
> When Scott pointed out that, without a pump, the amount of pipe within
> the fermenter may not be adequate for the amount of heat to be moved, he
> may well have hit the nail on the head, but I'd like to see if I can
> locate some precise figures or a formula or something like that. That
> was one of the main questions that I'm researching -- how efficient is a
> heat pipe, and how can I build or acquire one if one should work? The
> question has never, in my mind, been about the peltier.
>

If you're interested in peltier cooling somebody pointed out this product a
while back and you could skip the need for a heat pipe. I even emailed the
company asking about price but it was a bit more than I was interested in
spending. If I read their info correctly it looks like one would chill a 5
gal batch about 10 degrees below ambient. I could hit 65 degrees easy with
that mounted into the side of my fermenter.
http://www.coolworksinc.com/coolworks_products.htm

Mark R

On 21-Feb-2006, "Mark R" > wrote:

> > When Scott pointed out that, without a pump, the amount of pipe within
> > the fermenter may not be adequate for the amount of heat to be moved, he
> > may well have hit the nail on the head, but I'd like to see if I can
> > locate some precise figures or a formula or something like that. That
> > was one of the main questions that I'm researching -- how efficient is a
> > heat pipe, and how can I build or acquire one if one should work? The
> > question has never, in my mind, been about the peltier.
> >
>
> If you're interested in peltier cooling somebody pointed out this product
> a
> while back and you could skip the need for a heat pipe. I even emailed the
> company asking about price but it was a bit more than I was interested in
> spending. If I read their info correctly it looks like one would chill a 5
> gal batch about 10 degrees below ambient. I could hit 65 degrees easy with
> that mounted into the side of my fermenter.
> http://www.coolworksinc.com/coolworks_products.htm
>
> Mark R

I bought a peltier cooling module from these people at
http://www.mpja.com/listitems.asp?dept=60. Some day (when I get around to
it), I'm gonna build an insulated box for my fermenter, and use this thing
to cool it (or rather keep it at a cooler temperature).

If I recall correctly, these things only move abot 80-90 BTU/HR. That would
be OK to maintain a lower temperature, but wouldn't do much to cool hot wort
(that's about the same as adding 3/4 lb of ice every hour).

-Hershel

> how efficient is a heat pipe, and how can I build or acquire one if one
> should work? The question has never, in my mind, been about the peltier.

Efficient in what terms that you are trying to maximize/minimize? Energy?
Amount of tubing required? The latter was my point. That you'll require a
very large heat sink (heat pipe) to be effective.

I think you have way too much time on your hands... a single wet towel
and a fan will work much better for a 5 gallon carboy



Bill Velek wrote:

> I've been kicking an idea around for awhile and did a google-search but
> couldn't find anything directly on point. A recent post about peltier
> devices made me think about this again. What about coupling a peltier
> with a heatpipe?
>
> For those who don't know, a 'heat pipe' is a very simple device with no
> moving parts and requiring no power, but which helps transfer heat from
> one place to another. In its simplest form, it would be a length of
> straight copper pipe sealed at both ends, partially filled with alcohol
> or freon or some other liquid to act as a refrigerant. To cool a
> carboy, it would be inserted into the neck of the carboy and extend from
> the bottom and protrude through the neck for some distance -- perhaps a
> foot (30cm) or a bit more. The liquid refrigerant (alcohol, freon, or
> whatever) pools at the bottom of the pipe, picks up heat from the
> fermenti

Damn you're good, Joe <grin>.

Circulating the wine during fermentation will improve heat transfer to
the heat pipe. But that circulation will also cause the yeast to
undergo frequent temperature excursions (which makes them not so happy),
and the circulation will affect extraction of tannins and phenols and
other stuff from skins in fermenting reds (oh the variables one must
consider).

By the way, cooling liquids with submerged heat exchange tubing induces
temperature gradients in the must. The bulk liquid will be a few (to
several) degrees warmer than the liquid in contact with the cooling
tubing, depending on the surface temperature of the tubing.

Gene

Joe Sallustio wrote:

> We used to use peltier devices as a passive cooling system for the
> military back in the 60's. We built the first ones where I used to
> work; they were heat pipes in effect. They are not very efficient from
> an electricity usage standpoint, are affected by ambient conditions;
> they are rated by temperature across the faces at a given current.
>
> You did hit the nail on the head when you questioned the heat transfer
> required if placed into a carboy. Your surface to mass ratio with any
> material is too low if you intend to insert it into a carboy. You
> can't use copper or copper bearing alloys in winemaking as you know
> from others so the thermal conductivity will be lower to make matters
> worse.
>
> If you wrap the tubing around the carboy that might be another matter
> but all of this would turn out to be an expensive proposition.
>
> If you live in an area where the relative humidity is low the
> evaporative cooling idea sounds good, you could wrap a towel around the
> carboy and drip water onto it and blow a fan across it to improve the
> efficiency.
>
> If you are willing to pump fluid you may be able to place a tank in a
> refrigerator or freezer and pump fluid out through copper tubing
> wrapped around a carboy foamed over with an insulation package.
>
> I apologize for not giving you values but I just can't see it working;
> you can gather thermal conductivity data from the CRC handbooks, any
> version would do. That won't be the issue. The available surface area
> of the tubing inserted and in contact with the wine will be the issue
> no matter how cold you can get the liquid in the tubing or how fast it
> flows.
>
> Joe
>
>
>>So long as the reduced thermal conductivity doesn't present a problem,
>>stainless would be fine in place of copper.
>>
>>When Scott pointed out that, without a pump, the amount of pipe within
>>the fermenter may not be adequate for the amount of heat to be moved, he
>> may well have hit the nail on the head, but I'd like to see if I can
>>locate some precise figures or a formula or something like that. That
>>was one of the main questions that I'm researching
>
>

"Hershel Roberson" > wrote in message
>
> If I recall correctly, these things only move abot 80-90 BTU/HR. That
would
> be OK to maintain a lower temperature, but wouldn't do much to cool hot
wort
> (that's about the same as adding 3/4 lb of ice every hour).
>

Use a wort chiller to bring the hot wort down to fermentation temps. Then
wrap the fermenter in a blanket and plug in the peltier. If house ambient is
around 73 and one unit chills a 10 gallon aquarium 6-8 degrees (and remember
there is lots of uninsulated surface area on an aquarium) it should keep 5
plus gallons in the 64 to 68 range somewhere. Now if you sprayed foam
insulation on the outside of your fermenter you may get it down even lower.
The problem I see is they have only two controllers, one in the 45-65 range
and one from 65-85. You'll either operate one at the bottom of it's scale,
or if you use the other and have problems maintaining 64 degrees, it could
run all the time.

Mark R

> Circulating the wine during fermentation will improve heat transfer to the
> heat pipe. But that circulation will also cause the yeast to undergo
> frequent temperature excursions (which makes them not so happy), and the
> circulation will affect extraction of tannins and phenols and other stuff
> from skins in fermenting reds (oh the variables one must consider).

I believe we are talking about circulating the coolant in the chiller lines,
and not circulating the beverage. At least that's what I was referring to
when I mentioned recirculation.

>I think you have way too much time on your hands... a single wet towel and
>a fan will work much better for a 5 gallon carboy

That's not nearly enough cooling for where I live. I've certainly thought
about doing the same thing for the same reasons, but not for a 10F drop tops
that you can achieve with the wet towel and fan method. I need to drop 25F
and hold it from ambient during our very long summers here in San Diego.

Plus, brewers are gadget geeks. Does anyone need a better reason to make a
new toy for brewing?

Scott Lindner > wrote:
>Plus, brewers are gadget geeks. Does anyone need a better reason to make a
>new toy for brewing?

That only holds true for some brewers. See the "sparge arm"
thread in rcb-- some of us still enjoy doing things using very
simple procedures and equipment.
--
Joel Plutchak "People who drink wine with barbecue deserve to be
plutchak@[...] jeered at and socially ostracized." - Mike Stewart

Scott Lindner wrote:
>> I think you have way too much time on your hands... a single wet towel and
>> a fan will work much better for a 5 gallon carboy
>
> That's not nearly enough cooling for where I live. I've certainly thought
> about doing the same thing for the same reasons, but not for a 10F drop tops
> that you can achieve with the wet towel and fan method. I need to drop 25F
> and hold it from ambient during our very long summers here in San Diego.
>
> Plus, brewers are gadget geeks. Does anyone need a better reason to make a
> new toy for brewing?
>
>
Why not use an old fridge?? it will give you the temperature control you
need (you may need to tweak the thermostat to get it to go a bit higher)
but it will be stable and quite cheap to run as it is already insulated.
Ben.

> That only holds true for some brewers. See the "sparge arm"
> thread in rcb-- some of us still enjoy doing things using very
> simple procedures and equipment.

I did intend that to be a comment for some of us, and not all of us. We all
brew for different reasons.

> Why not use an old fridge?? it will give you the temperature control you
> need (you may need to tweak the thermostat to get it to go a bit higher)
> but it will be stable and quite cheap to run as it is already insulated.

That's been my feeling for the past couple of months. I'm about to move to
a new house. I see a fermentation shed in the back already. :-)

That's what I do, it works great.

Joe

For completeness of the discussion, I spoke about the 'other'
circulation possibility (i.e. circulating the must). Yes, I was aware
you were speaking about recirculating the coolant in the chiller lines.

Thanks for noticing.
Gene

Scott Lindner wrote:
>>Circulating the wine during fermentation will improve heat transfer to the
>>heat pipe. But that circulation will also cause the yeast to undergo
>>frequent temperature excursions (which makes them not so happy), and the
>>circulation will affect extraction of tannins and phenols and other stuff
>>from skins in fermenting reds (oh the variables one must consider).
>
>
> I believe we are talking about circulating the coolant in the chiller lines,
> and not circulating the beverage. At least that's what I was referring to
> when I mentioned recirculation.
>
>

I originally cross-posted this to r.c.m and r.c.w., in addition to the
beer brewing groups, because I know that we all use carboys and other
fermenters, and believed that we are all concerned with heat. Judging
from the replies, it looks like there have been many responses from
r.c.w., but since it is fairly clear that my idea is less likely to
work with wine (and possibly not mead), all future posts by me on this
subject will be limited to the beer groups, i.e., this will be my last
post on this to r.c.m and r.c.w. However, I do want to take this
opportunity to thank everyone, and to let you all know that I will be
responding further to some posts by Joe Sallustio, gene, Mark R, Hershel
Roberson, Scott Linder, Droopy, QD Steve, and Ben -- but only through
the beer forums; I don't know which of you are subscribed to them, and
if any of you belong only to r.c.m. or r.c.w. but are particularly
interested in discussing this further, I'll be happy to include you in
direct emails if you don't want to visit the beer groups.

Meanwhile, let me just end here with a few general statements that some
of you might find interesting or useful.

First, based on further research, I still think this device might work,
and actually work well enough to even permit _lagers_ to be made in an
unrefrigerated carboy -- dropping the temp down close to freezing. I
will explain why in a longer post on r.c.b., a.b.h-b., and a.h.

Second, "Heat pipes have an effective thermal conductivity _many_
_thousands_ of times that of copper", and they are used in a wide range
of applications, from refrigerators and air-conditioners to even lap
tops computers.

Third, even water can be used as a refrigerant inside of a heat pipe,
although alcohol has a more useful range for my idea.

Here's a link for some of the above:
http://www.cheresources.com/htpipes.shtml

And now I just have a quick reply for Mike, below.

Mike McGeough wrote:

> Bill ,

snip

> My one thought on your heat pipe setup is that you might well want to
> limit the contact between copper and an acid medium like wine.

snip

Understood. Because I don't think stainless steel is a viable option,
the only other solution I can think of regarding wine is to possibly
coat the heat-pipe with something like very thin plastic -- maybe a
food-grade plastic paint -- but I don't know how much of an effect that
would have on the efficiency of the heat pipe. Also, it might well be
that there is never a need to drop wine fermentation temp down that far,
so please excuse me if I was out of line to post in your forums.

> Sounds like fun though. Let us know how it turns out.

If I decide to proceed further and manage to get one built and working
well, I'll post a final report in your wine and mead forums just to let
everyone know.

Cheers, Bill Velek
Join "HomeBrewers" international grid-computing team and help mankind by
donating spare computer power for medical research such as cancer; we're
in the top 7%, and we beat the MillerTime team: http://tinyurl.com/b7ofs
The life that your computer can help save ... might be someone you love.

Bill Velek wrote: (months ago)
> Rob wrote:
>
>> True, but stainless would work, and there are folks who sell steel
>> Hypodermic Needle tubing with very thin walls.
>>
>> Personally, not a big problem for me, but I live where it usually isn't
>> too hot outside during fermentation season, and my batches aren't big
>> enough to need such cooling.
>> Very cool idea, though.
>>
>> Rob
>
>
> Thanks, Rob, for the encouraging words. Also a thank you to Mike and
> Droppy for pointing out the problem with copper, and to the other
> posters for their comments, too. I'll just cover everything in this one
> post.
>
> So long as the reduced thermal conductivity doesn't present a problem,
> stainless would be fine in place of copper.
>
> When Scott pointed out that, without a pump, the amount of pipe within
> the fermenter may not be adequate for the amount of heat to be moved, he
> may well have hit the nail on the head, but I'd like to see if I can
> locate some precise figures or a formula or something like that. That
> was one of the main questions that I'm researching -- how efficient is a
> heat pipe, and how can I build or acquire one if one should work? The
> question has never, in my mind, been about the peltier.

What no one mentioned about a heat pipe is how they work. When a heat
pipe is working as intended, heat at the bottom boils the working fluid,
which rises as a vapor to the top where it condenses and heats the
condenser while cooling the working fluid. The transition from liquid to
gas and back is called the heat of vaporization, and it's large compared
to convection which is all you get if you don't boil the fluid.

I heat my house with heat pipes, the working fluid boils at the bottom
of the pipe, rises and condenses. It's called steam heat and was
installed when my house was new, about 1895. All it takes is heat and
gravity, so it's dead reliable.

As a cooler there are many problems, however. You absolutely need the
state change to make any appreciable heat flow, so you need a heat pipe
with a working fluid which boils at or below the target temperature, say
32F to 55F depending on what yeast and process you want to use. Needless
to say there aren't many heat pipes which function at that range, so you
need to find such a thing before going to step two.

There was a lot of calculation of watts and BTU which was very confused.
A BTU is a unit of heat, a watt is a rate of heat. They don't directly
without bringing time into or out of the calculation, in watt-hr or
BTU/hr. In any case it's irrelevant, the cooling you need depends on
insulation, wrap the carboy in copper pipe, pack it in foam, and a very
small cooler will do it. The idea of an old fridge is good, adding a
bunch of insulation will drop the cost of operation by a bunch. It
doesn't need to be pretty, yeast don't give style points.

On peltier junctions: there's a curve of temperature flow (BTU/hr)
between the ends based on power applied. It's largely immune to
temperature, so a ten degree head of 40-50F will take about the same
power as 55-65F. It's hard to get a big temperature delta with peltier,
lots of info on the topic.

Standard cooling methods are very efficient. When you see an air
conditioner labeled as EGR of 10, it means it pumps 10 BTU/hr for every
1 BTU/hr of electricity used (293mw = 1 BTU/hr). Peltier is quiet,
reliable, but not particularly efficient. The old refrigerator approach
is a good one, even if it's not as fun as heat pipes and peltier.

--
bill davidsen >
Beer blog: http://blogs.tmr.com/beer
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